Motor vehicle lighting device implementing a function for writing on the ground

ABSTRACT

The invention proposes a lighting device for a motor vehicle, including a first lighting module adapted to project a pixelized first beam with a first resolution and a second lighting module adapted to project a pixelized low beam type second beam with a second resolution lower than the first resolution, the first and second lighting modules being such that the first and second beams overlap vertically at least in part to form a global beam, the device including a control unit able to control selectively a plurality of pixels of the first and second beams so as to project a motif in the global beam.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/374,207filed on Apr. 3, 2019 and entitled, “Motor Vehicle Lighting DeviceImplementing a Function for Writing on the Ground.” This previousapplication is incorporated herein by reference.

BACKGROUND Technical Field

The invention relates to the field of lighting and/or signalling lights,in particular for motor vehicles. The invention more particularlyconcerns a lighting device for motor vehicles able to project apixelized light beam in order to project onto the road information forthe driver of the vehicle.

Discussion of Related Art

In order for the information that this device projects onto the road tobe clearly perceptible for the driver, it is necessary for the pixelizedlight beam to have a particularly high resolution. However, thetechnologies necessary for achieving such resolutions are costly, inparticular when it is required to obtain a wide light beam, which isobligatory in the case of a low beam type beam.

In order to reduce the price of the lighting device, it has thereforebeen proposed, for example in the patent document EP 2 772 682, todivide the low beam type beam into a basic beam on which a pixelizedbeam of small size is superimposed. As a result, the global beam has anacceptable horizontal amplitude for a low beam type beam and a pixelizedzone that can be used for motif projection in that global beam, bycontrast between that pixelized zone and the basic beam.

Although this solution actually makes it possible to optimize the costof the lighting device, it nevertheless gives rise to a problem when itis wished to implement a function of dynamic lighting of turns. Thatfunction consists in modifying the luminous characteristics of the lowbeam type beam when the vehicle enters a turn to improve the view of thedriver in the turn without dazzling the other users of the road. Forexample the horizontal amplitude of the low beam type beam is increasedin the direction of the turn or the intensity maximum of the low beamtype beam is moved in the direction of the turn.

Now in this case, because of the modification of the luminouscharacteristics of the basic beam, it is possible for the contrastbetween the pixelized zone and the basic beam not to be sufficient toenable the driver to perceive the motif projected in the global beam orfor this contrast to change suddenly, causing a sudden modification ofthe pattern that may prove disturbing for the driver.

SUMMARY

An object of the invention is to alleviate this problem and moreprecisely to propose a solution enabling projection of a motif in a lowbeam type beam, that motif remaining perceptible without suddenmodification on use of a dynamic turn lighting function.

To this end, the invention proposes a lighting device for a motorvehicle, including a first lighting module adapted to project apixelized first beam with a first resolution and a second lightingmodule adapted to project a pixelized low beam type second beam with asecond resolution lower than the first resolution, the first and secondlighting modules being such that the first and second beams verticallyoverlap at least partly to form a global beam, the device including acontrol unit able to control selectively a plurality of pixels of thefirst and second beams so as to project a motif in the global beam.

According to the invention, the control unit is adapted to control atleast one pixel of each of the first and second beams when the motorvehicle enters a turn so as to create a movement of said motif in theglobal beam.

Thanks to the invention, the motif is moved simultaneously with themovement of the characteristics of the global beam so that the contrastbetween the first and second light beams enabling generation of thatmotif remains constant when the dynamic turn lighting function is used.The perceptibility of the motif is therefore guaranteed, with no suddenvariation of contrast.

Advantageously, the first and second lighting modules are such that thepixelized first beam includes a number of pixels greater than the numberof pixel of the pixelized low beam type second beam; and/or each pixelof the pixelized first beam has a width and/or a length strictly lessthan the minimum width and/or the minimum length respectively of thepixels of the pixelized low beam type second beam; the pixelized firstbeam has a horizontal amplitude less than the horizontal amplitude ofthe pixelized low beam type second beam.

There is meant by the pixel width, respectively the pixel length, thewidth, respectively the length, of that pixel when it is projected ontothe road or onto a screen disposed for example at 25 metres from thelighting device. These dimensions, measured in degrees, correspond tothe angular apertures of the elementary beams that can be activatedselectively and that compose the pixelized first and second beams.

The resolution of the pixelized first and second beams can therefore beestimated on the basis of the number and the dimensions of the pixelsconstituting those beams relative to the amplitudes of those beams.

According to one embodiment, the first lighting module may be such thatthe pixelized first beam includes at least 400 pixels, or even at least1000 pixels, or even at least 2000 pixels. This pixelized first beam mayfor example include 20 columns and 20 lines of pixels, in particular 32columns and 32 lines of pixels.

The first module may advantageously be such that each pixel of thepixelized first beam has a width and/or a length less than 1°, inparticular less than 0.5°, or even less than 0.3°.

Also advantageously, the first lighting module may be such that thepixelized first beam has a vertical amplitude of at least 5°, inparticular at least 9°, and a horizontal amplitude of at least 5°, inparticular at least 12°.

The first module may for example include: a pixelized light sourceincluding a plurality of elementary emitters arranged as a matrix, eachof the elementary emitters being activatable selectively to emit anelementary light beam; and a projection optical element associated withsaid pixelized light source to project each of said elementary lightbeams in the form of a pixel, the set of pixels forming said pixelizedbeam.

The projection optical element is advantageously such that the pixelizedbeam has a vertical amplitude of at least 5° and a horizontal amplitudeof at least 5°. These horizontal and vertical amplitudes make itpossible to ensures that the pixelized beam is projected onto an area ofthe road that is sufficiently vast to implement functions of writing onthe road by projection of a motif in this pixelized beam, and inparticular ground marking display functions, driving assistancefunctions, and GPS information projection functions, or again adaptivelighting functions necessitating pixelization of the light beam and inparticular non-dazzle high beam lamp type lighting functions or dynamicturn lighting type lighting functions. The projection optical elementmay therefore comprise one or more of the following optical components:lens, reflector, guide, collimator, prism.

If necessary, the pixelized light source may include at least 20 columnsand at least 20 lines of elementary emitters, in particular at least 32lines and columns of elementary emitters. These minimum numbers ofcolumns and lines of elementary emitters, in combination with thevertical and horizontal amplitudes mentioned above, make it possible toobtain for each of the elementary light beams, when projected by theprojection optical element, an angular aperture less than 0.5°, or evenless than 0.3°. As a result a minimum resolution of the pixelized beamis obtained when it is projected onto the road that guaranteessatisfactory perception of said projected motif in the pixelized beam bya user of the road and/or by the driver of the vehicle equipped in thisway.

The elementary emitters and the projection optical element areadvantageously such that two adjacent pixels, i.e. two adjacent pixelson the same line or in the same column, are contiguous, i.e. theiradjacent edges coincide.

In one embodiment of the invention, the pixelized light source of thefirst module comprises at least one matrix of electroluminescentelements (termed a monolithic array) arranged in at least two columns byat least two lines. The electroluminescent source preferably comprisesat least one matrix of monolithic electroluminescent elements, alsotermed a monolithic matrix.

In a monolithic matrix, the electroluminescent elements are grown from acommon substrate and are electrically connected so as to be activatableselectively, individually or in subsets of electroluminescent elements.Thus each electroluminescent element or group of electroluminescentelements may form one of the elementary emitters of said pixelized lightsource that is able to emit light when its or their material is fed withelectricity.

Various arrangements of electroluminescent elements can conform to thismonolithic matrix definition, provided that the electroluminescentelements have one of their principal lengthwise dimensions substantiallyperpendicular to a common substrate and the distance between theelementary emitters formed by one or more electroluminescent elementselectrically grouped together is short compared to the distances imposedin known arrangements of flat square chips soldered onto a printedcircuit card.

The substrate may consist mostly of semiconductor material. Thesubstrate may include one or more other materials, for examplenon-semiconductor materials.

These electroluminescent elements, of submillimetre size, are forexample arranged projecting from the substrate so as to form rods ofhexagonal section. The electroluminescent rods arise from a first faceof a substrate. Each electroluminescent rod, formed here using galliumnitride (GaN), extends perpendicularly or substantially perpendicularly,projecting from the substrate, here based on silicon, other materialssuch as silicon carbide being usable without departing from the scope ofthe invention. For example, the electroluminescent rods could beproduced from an alloy of aluminium nitride and gallium nitride (AlGaN)or from an alloy of phosphides of aluminium, indium and gallium(AlInGaP). Each electroluminescent rod extends along a lengthwise axisdefining its height, the base of each rod being disposed in a plane ofthe upper face of substrate.

The electroluminescent rods of the same monolithic matrix advantageouslyhave the same shape and the same dimensions. Each is delimited by an endface and by a circumferential wall that extends along the lengthwiseaxis of the rod. When the electroluminescent rods are doped andsubjected to polarization, the resulting light that exits thesemiconductor source is emitted essentially from the circumferentialwall, it being understood that light rays may also exit from the endface. As a result each electroluminescent rod acts as a singleelectroluminescent diode and the brightness of this source is improvedon the one hand by the density of the electroluminescent rods presentand on the other hand by the size of the illuminating surface defined bythe circumferential wall and which therefore extends over all theperimeter and all the height of the rod. The height of a rod may bebetween 2 and 10 μm inclusive, preferably 8 μm; the greatest dimensionof the end face of a rod is less than 2 μm, preferably less than orequal to 1 μm.

Clearly, during the formation of the electroluminescent rods, the heightmay be modified from one zone of the pixelized light source to another,so as to increase the brightness of the corresponding zone if the meanheight of the rods constituting it is increased. Thus a group ofelectroluminescent rods may have a height or heights different fromthat/those of another group of electroluminescent rods, these two groupsbeing constituents of the same semiconductor light source comprisingelectroluminescent rods with submillimetre dimensions. The shape of theelectroluminescent rods may also vary from one monolithic matrix toanother, in particular the sections of the rods and the shape of the endface. The rods have a cylindrical general shape and may in particularhave a polygonal, and more particularly hexagonal section shape. Clearlyit is important that light can be emitted through the circumferentialwall, whether the latter has a polygonal or circular shape.

Moreover, the end face may have a substantially plane shapeperpendicular to the circumferential wall so that it extendssubstantially parallel to the upper face of the substrate, or may have aconvex or pointed shape at its centre so as to multiply the directionsof emissions of the light exiting from this end face.

The electroluminescent rods are arranged in a two-dimensional matrix.This arrangement could be such that the rods are arranged in a quincunx.As a general rule the rods are disposed at regular intervals on thesubstrate and the distance separating two immediately adjacentelectroluminescent rods in each of the dimensions of the matrix must beat the minimum equal to 2 μm, preferably between 3 μm and 10 μminclusive, in order for the light emitted by the circumferential wall ofeach rod to be able to exit the matrix of electroluminescent rods.Moreover, these separation distances measured between two lengthwiseaxes of adjacent rods do not exceed 100 μm.

According to another embodiment, the monolithic matrix may includeelectroluminescent elements formed by epitaxially grown layers ofelectroluminescent elements, in particular a first layer of n-doped GaNand a second layer of p-doped GaN, on a single substrate, for example ofsilicon carbide, that is cut (by milling and/or ablation) to form aplurality of elementary emitters arising from the same substrate. Adesign of this kind results in a plurality of electroluminescent blocksall arising from the same substrate and electrically connected to oneanother so as to be activatable selectively.

In one example of this other embodiment, the substrate of the monolithicmatrix may have a thickness between 100 μm and 800 μm inclusive, inparticular equal to 200 μm; each block may have a width and a lengtheach between 50 μm and 500 μm inclusive, preferably between 100 μm and200 μm inclusive. In a variant the length and the width are equal. Theheight of each block is less than 500 μm, preferably less than 300 μm.Finally, the exit surface of each block may be formed through thesubstrate, on the side opposite the epitaxial growth. The distancebetween contiguous elementary emitters may be less than 1 μm, inparticular less than 500 nm, and is preferably less than 200 nm.

According to another embodiment that is not shown, also withelectroluminescent rods projecting from the same substrate, as describedabove, or with electroluminescent blocks obtained by cutting superposedelectroluminescent layers on the same substrate, the monolithic matrixmay further include a layer of a polymer material in which theelectroluminescent elements are at least partly buried. This layer maytherefore extend over the whole of the substrate or only around aparticular group of electroluminescent elements. The polymer material,which may in particular be based on silicone, creates a protective layerthat makes it possible to protect the electroluminescent elementswithout impeding the diffusion of the light rays. Moreover, it ispossible to integrate into this layer of polymer material wavelengthconversion means, for example luminophores, able to absorb at least someof the rays emitted by one of the elements and to convert at least someof said absorbed excitation light into emitted light at a wavelengthdifferent form that of the excitation light. The luminophores mayinterchangeably be buried in the mass of the polymer material ordisposed on the surface of the layer of that polymer material.

The pixelized light source may further include a reflective materialcoating to deviate the light rays toward the exit surfaces of the lightsource.

The electroluminescent elements with submillimetre dimensions define aparticular exit surface in a plane substantially parallel to thesubstrate. Clearly the shape of that exit surface is defined as afunction of the number and the arrangement of the electroluminescentelements that constitute it. A substantially rectangular shape of theemission surface can thus be defined, it being understood that thelatter may vary and assume any shape without departing from the scope ofthe invention.

The monolithic matrix or matrices adapted to emit light rays may becoupled to the control unit. The control unit may be mounted on one ormore matrices, the combination thus forming a lighting submodule. Inthis case, the control unit may include a central processor unit coupledto a memory in which is stored a computer program that comprisesinstructions enabling the processor to execute steps generating signalsfor controlling the light source. The control unit may be an integratedcircuit, for example an application-specific integrated circuit (ASIC)or an application-specific standard product (ASSP).

Alternatively, the pixelized light source may be formed by assembling atleast one light source formed of at least one electroluminescent diodeemitting light and a matrix of optoelectronic elements, for example amatrix of micromirrors (also known as a digital micromirror device(DMD)) that reflects the light rays from said at least one light sourcetoward the projection optical element. If necessary, a collectionoptical element enables collection of the rays from the at least onelight source in order to concentrate them and to direct them toward thesurface of the micromirror matrix. Each micromirror is able to pivotbetween two fixed positions, a first position in which the light raysare reflected toward the projection optical element and a secondposition in which the light rays are reflected in a different directionto the projection optical element. The two fixed positions are orientedin the same manner for all the micromirrors and form relative to areference plane supporting the micromirror matrix an angle that ischaracteristic of the micromirror matrix and defined in itsspecifications. That angle is generally less than 20° and usually has avalue of approximately 12°. Thus each micromirror reflecting a smallportion of the light rays incident on the micromirror matrix forms anelementary emitter of the pixelized light source, actuation and changeof position control enabling selective activation of this elementaryemitter to emit or not an elementary light beam.

In another variant, the pixelized light source may be formed by a laserscanning system in which a laser source emits a laser beam towardsscanning means configured to scan with the laser beam the surface of awavelength converter element, which surface is imaged by the projectionoptical element. The beam is scanned by the scanning means at a speedsufficiently high for the human eye not to perceive its movement in theprojected image. The synchronized control of the lighting of the lasersource and the movement of scanning the beam enables generation of amatrix of elementary emitters activatable selectively at the level ofthe surface of the wavelength converter element. Here the scanning meansconsist of a mobile micromirror enabling scanning of the surface of thewavelength converter element by reflection of the laser beam. Themicromirrors mentioned as scanning means may for example be ofmicro-electro-mechanical system (MEMS) type. However, the invention isin no way limited to these scanning means and may use other kinds ofscanning means such as a series of mirrors arranged on a rotary element,the rotation of the element causing the scanning of the transmissionsurface by the beam laser.

If necessary the second lighting module may be such that the pixelizedlow beam type second beam includes between 5 and 400 pixels, inparticular 9 pixels.

For example, the pixelized low beam type second beam may include asingle line of pixels or instead a plurality of lines of pixels disposedone on top of the other.

The second module may advantageously be such that each pixel of thepixelized low beam type second beam has a width and/or a length strictlygreater than 0.5°, and in particular greater than 1°.

Again advantageously, the second lighting module may be such that thepixelized low beam type second beam has a vertical amplitude of at least5° and a horizontal amplitude of at least 15°.

By low beam type beam is meant a light beam intended to light the roadwithout dazzling the other users of the road. To this end, the secondlighting module is such that the pixelized low beam type second beam hasa low beam type upper cut-off, that upper cut-off being defined by theupper edges of the pixels constituting the uppermost line of this secondlight beam.

The low beam type upper cut-off may for example include a horizontalportion and an oblique portion. See for example ECE regulation n° 123which defines a regulatory cut-off including a horizontal portion at0.57° above the horizon and an oblique portion inclined at 15° relativeto the horizontal portion.

The low beam type upper cut-off may instead include a single flathorizontal portion.

In one embodiment of the invention, the first and second lightingmodules are such that the first and second beams overlap so that thepixelized first beam extends in the global beam exclusively below theupper cut-off of the pixelized low beam type second beam.

If necessary, the global beam includes an upper horizontal cut-offformed exclusively by the upper horizontal cut-off of the pixelized lowbeam type second beam. In this case, the pixelized first beam istherefore completely enclosed within the pixelized low beam type secondbeam and the vertical overlap is then total. There is therefore obtainedthe benefit of a projection zone entirely dedicated to a writing on theroad function and it is guaranteed that in the event of a problem at thelevel of the first module the totality of the low beam lighting functionis retained.

In another embodiment of the invention, the first and second lightingmodules are such that the first and second beams overlap so that thepixelized first beam extends in the global beam above and below theupper cut-off of the pixelized low beam type second beam.

If necessary, the portion of the pixelized first beam extending abovethe pixelized low beam type second beam may produce a portion, forexample an oblique portion, of a low beam type cut-off intended to beassociated with the upper cut-off of the second beam. In this case, thisportion may for example be moved when the vehicle enters a turn toimprove the performance of the dynamic turn lighting function. Also,this portion of the pixelized first beam extending above the pixelizedlow beam type second beam is able to produce a selective high beam typelighting function.

The second lighting module is advantageously such that the pixelized lowbeam type second beam extends horizontally and substantiallysymmetrically on respective opposite sides of a vertical axis and thefirst lighting module is such that the pixelized first beam extendshorizontally and substantially asymmetrically on respective oppositesides of that vertical axis. This vertical axis may for example be avertical axis intersecting the optical axis of said lighting device. Inthe case of a pixelized low beam type second beam including a horizontalcut-off portion and an oblique cut-off portion the vertical axis may inparticular pass through the junction of these two horizontal and obliqueportions.

The pixelized first beam may preferably extend horizontally mostly onthe vehicle exterior side when the lighting device is mounted on thevehicle. It is therefore guaranteed that the projection zone for thewriting on the ground function is sufficiently extensive for the motiveto be movable whatever the curvature of the turn entered by the vehicle.

The first and second lighting modules are advantageously such that atleast one edge of each pixel of the pixelized first beam coincides withan edge of a pixel of the pixelized low beam type second beam.

By coincident pixel edges is meant a superposition of those edges whenthe pixels are projected onto the road or onto a screen disposed forexample at 25 metres from the lighting device. The first and secondlighting modules are preferably such that at least one vertical edge ofeach pixel of the pixelized low beam type second beam coincides with avertical edge of a pixel of the pixelized low beam type first beam. Ifnecessary, the width of the pixels of the second beam is madeproportional to the width of the pixels of the first beam. It is thuspossible to obtain an overlap of the first and second beams withinterleaving of the pixels so that the global beam has a satisfactoryhomogeneity, that is to say with no non-homogeneity between two pixelsof the global beam.

The control unit is advantageously adapted to control selectively theluminous intensity of said plurality of pixels of the first and secondbeams so that the motif is projected in the global beam by a differenceof intensity between those pixels of the first and second light beams.

There is meant by controlling the luminous intensity of a pixel lightingor extinguishing that pixel and under-intensification orover-intensification of the luminous intensity of that pixel.

The motif that is intended to be projected is advantageously defined bya matrix of points and the control unit is adapted to controlselectively the luminous intensity of a plurality of pixels of the firstand second beams situated in a projection zone situated at the level ofthe overlap of the first and second beams so as to generate a contrastbetween each pair of pixels of that plurality of pixels that overlap,each contrast corresponding to a point of said matrix of points.

In other words, the overlap of the pixelized first and second beamsdefines a ix projection zone that can be controlled to display a motiftherein.

If necessary the motif may be generated by positive contrasts, i.e. bypositive intensity differences in each pair of pixels between the pixelof the first beam and the pixel of the second beam, for example byover-intensification of the pixel of the first beam and/or byunder-intensification of the pixel of the second beam.

The motif may instead be generated by negative contrasts, i.e. bynegative intensity differences in each pair of pixels between the pixelof the first beam and the pixel of the second beam for example byunder-intensification of the pixel of the first beam and/or byover-intensification of the pixel of the second beam.

If required, the control unit is adapted to reduce the luminousintensity of all the pixels of the pixelized low beam type second beamat the level of said projection zone. If necessary, the luminousintensity of the rest of the pixels of the pixelized low beam typesecond beam outside of the projection zone remains unchanged. Thecontrast and therefore the perceptibility of the pattern relative to therest of the pixelized low beam type second beam is therefore improved.

According to one embodiment of the invention, the control unit isadapted to control the pixels of the first beam and/or of the secondbeam when the motor vehicle enters a turn so as to modify the luminousintensity of the global beam in the direction of the turn. If necessarythe control unit is adapted to control the pixels of the first beamand/or the second beam when the motor vehicle enters a turn:to increasethe horizontal amplitude of the global beam in the direction of theturn, the pixels of the global beam being for example progressively litor over-intensified in the direction of the turn, and/or to move themaximum intensity of the global beam in the direction of the turn,and/or to move a portion of an upper cut-off, in particular an obliqueportion of an upper cut-off, of the global beam in the direction of theturn.

The control unit is advantageously adapted to control selectively theluminous intensity of said plurality of pixels of the first and secondbeams situated in the projection zone so as to move each contrastbetween a pair of pixels of that plurality of pixels that overlap towardanother pair of pixels of that plurality of pixels that overlap in thedirection of the turn. There is meant by movement of a contrast of afirst pair of pixels to a second pair of pixels controlling that secondpair of pixels so that the contrast of that second pair is substantiallyidentical to that of the first pair. This therefore guarantees thepreservation of the contrast on the movement of the motif so as to notto disturb the driver.

The lighting device advantageously includes a third lighting moduleadapted to project a pixelized high beam type third beam, the first andthird lighting modules being such that the first and third beamsvertically overlap at least partially.

The invention also consists in a lighting system for a motor vehicle,the system including a lighting device according to the invention asdescribed above and a device for detection of a turn intended to betaken by the motor vehicle, the control unit of the lighting devicebeing adapted to receive information from said turn detection device andto control the pixels of the beams projected by the lighting modules ofthe lighting device as a function of said information.

The detection device may in particular be a video camera filming theroad with associated image processing software or a steering wheel anglesensor.

The system advantageously includes a device for detection of trafficconditions of the vehicle and/or for reception of information relatingto the traffic conditions of the vehicle, and the control unit isadvantageously adapted to receive information relating to those trafficconditions from said detection and/or reception device and to controlselectively said plurality of pixels of the first and second beams so asto project a motif in the global beam concerning said trafficconditions.

For example the detection and/or receiving device may be a video camera,a lidar, a GPS device, or a wireless receiver. If necessary, theinformation on detected or received traffic conditions may be thepresence or the absence of a marking on the ground, an optimumtrajectory to be taken by the vehicle, GPS navigation information, thepresence of a road sign, the presence of an obstacle or of a hazard orthe state of the traffic.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will be betterunderstood with the aid of the description of examples and of thedrawings in which:

FIGS. 1A and 1B show front and plan views of a lighting device accordingto a preferred embodiment of the invention;

FIG. 1C shows the light beams projected by the luminous device fromFIGS. 1A and 1B;

FIG. 2A shows the light beams projected onto the road by the lightingdevice from FIGS. 1A and 1B when the vehicle is travelling on a straightroad and FIG. 2B shows the light beams projected onto the road by thelighting device from FIGS. 1A and 1B when the vehicle enters a turn.

DETAILED DESCRIPTION

Unless specifically indicated to the contrary, technical featuresdescribed in detail for a given embodiment may be combined with thetechnical features described by way of nonlimiting example in thecontext of other embodiments described.

There has been represented in FIGS. 1A and 1B a lighting device 1according to one embodiment of the invention. That lighting deviceincludes a first lighting module 2 adapted to project a pixelized firstbeam HR and a second lighting module 3 adapted to project a pixelizedlow beam type second beam LB. The pixelized first and second beams HRand LB have been represented in FIG. 1C projected onto a screen situatedat 25 metres from the lighting device 1 and on which are shown ahorizontal axis H-H representing the horizon and a vertical axis V-Vperpendicular to the horizontal axis H-H and crossing the optical axis Xof the lighting device 1.

The first module 2 includes: a pixelized light source 21 including 900elementary emitters arranged in a matrix of 20 lines by 45 columns, eachof the elementary emitters being activatable selectively to emit anelementary light beam; and a projection optical element 22 associatedwith said light source to project each of said elementary light beams inthe form of a pixel having a width and a length of 0.3°.

The set of pixels projected by the first module 2 form said pixelizedfirst beam HR. That beam HR has a horizontal amplitude of 12° and avertical amplitude of 9°. It extends asymmetrically on respectiveopposite sides of the vertical axis V-V. In the present case, thelighting device 1 being a righthand headlamp of the vehicle, the beam HRextends 4° on the vehicle interior side and 8° on the vehicle exteriorside. It equally extends 4° above the horizontal axis H-H and 5° belowthe horizontal axis H-H.

In the embodiment described, the light source 21 comprises a matrix ofmonolithic electroluminescent elements as described above.

There may be provision for replacing the light source 21 by any othertype of pixelized light source described above, such as for example amatrix of electroluminescent diodes or a light source associated with amatrix of optoelectronic elements such as micromirrors.

The first lighting module may comprise elements other than thosedescribed above. Those elements will not be described in the context ofthe present invention because they do not interact functionally with thefeatures according to the invention.

The second module 3 includes: a matrix 31 of elementary emittersincluding 9 electroluminescent diodes activatable selectively andarranged along a line, each diode being able to emit an elementary lightbeam; a plurality 32 of primary optical elements disposed in front ofthe matrix 31 to collect, shape and guide the elementary light beamscoming from each of the electroluminescent diodes; and a projectionoptical element 33 disposed in front of the primary optical elements toproject each of said elementary light beams coming from the primaryoptical elements in the form of a pixel having a width of 3° and alength of 5°.

See in particular the document FR3056692 which describes the principleof operation of a module of this kind.

The pixels projected by the second module 3 form said pixelized secondbeam LB. This beam LB has a horizontal amplitude of 20° and a verticalamplitude of 8°.

The second lighting module 3 is such that the pixelized low beam typesecond beam has a low beam type upper cut-off LB_CO. In the presentcase, the primary optical elements 32 are arranged so that their exitsurfaces are abutted so that the lower edges of those surfaces join andare aligned and the projection optical element 33 is focused on theseexit surfaces. As a result, the projection optical element 33 comes toimage these lower edges in an upper cut-off LB_CO defined by the upperedges of the pixels constituting this second light beam.

In the example described, the upper cut-off includes a single flathorizontal portion disposed 0.57° below the horizontal axis H-H.

The pixelized second beam therefore forms a pixelized low beam typebeam.

It is therefore seen in FIG. 1C that: the pixelized first beam HRincludes a number of pixels greater than the number of pixels of thepixelized low beam type second beam LB; each pixel of the pixelizedfirst beam HR has a width and a length respectively less than the widthand the length of the pixels of the pixelized low beam type second beamLB; and the pixelized first beam HR has a horizontal amplitude less thanthe horizontal amplitude of the pixelized low beam type second beam LB.

It therefore follows that the resolution of the pixelized first beam HRis greater than the resolution of the pixelized low beam type secondbeam LB.

According to the invention, the first and second lighting modules 2 and3 are such that the first and second beams HR and LB vertically overlapin part to form a global beam LBG.

The pixelized first beam HR therefore extends above and below the uppercut-off LB_CO of the pixelized low beam type second beam LB.

The overlap is such that each vertical edge of each pixel of thepixelized low beam type second beam LB coincides with a vertical edge ofa pixel of the pixelized first beam HR.

Finally, the lighting device 1 includes a control unit 4 able to controlselectively the luminous intensity of each of the pixels of the firstand second beams HR and LB as a function of control instructions that itreceives, for example by selectively lighting, extinguishing theelementary emitters of the light sources 21 and 31 or again byincreasing or decreasing the electrical power supplied to each of theseelementary emitters.

The overlap of the pixelized first and second beams defines a projectionzone ZP formed by the overlapping of a plurality of pixels of thepixelized first and second beams HR and LB. Each pixel of the projectionzone ZP is therefore formed by a pair consisting of a pixel of the firstbeam HR and a pixel of the second beam LB that overlap one another. Thispixel of the projection zone ZP is consequently controllable by thecontrol unit 4, conjointly controlling the luminous intensity of eachpixel of the pair of pixels.

There has been represented in FIG. 2A a first operating mode of thelighting device 1 from FIGS. 1A to 1C. In this mode the vehicle equippedwith the lighting device 1 is travelling in a straight line. Thisvehicle is equipped with a device 5 for detecting a turn intended to betaken by the motor vehicle and a device 6 for detection and reception ofinformation relating to the traffic conditions of the vehicle.

The device 5 for detection of a turn detects that the vehicle istravelling in a straight line and the device 6 for detection ofinformation relating to the traffic conditions of the vehicle receivesGPS information to be transmitted to the driver via the lighting device1.

On the one hand, the control unit 4 controls a plurality of pixels ofthe pixelized low beam type second beam LB to light the entirety of theroad, the rest of the pixels of this second beam LB therefore remainingextinguished.

On the other hand, the control unit 4 controls a first plurality ofpixels LBK of the pixelized first beam HR extending above the cut-offLB_CO to complete the second beam LB and to form an oblique cut-offportion LBK_CO that is associated with the cut-off LB_CO to formconjointly a regulatory low beam type cut-off profile.

Finally, the control unit 4 controls a second plurality of pixels HRM ofthe pixelized first beam HR in the projection zone ZP so as to createlocal luminous over-intensifications in the pixels of the second beam LBwith which this second plurality of pixels HRM overlaps, the rest of thepixels of the pixelized first beam remaining extinguished. Theseover-intensifications therefore create positive contrasts thatconsequently form a motif in the projection zone that indicates to thedriver the direction to take.

In order to strengthen the contrast and to render the motif even moreperceptible, the control unit 4 reduces the luminous intensity of thepixels of the second beam LB with which the second plurality of pixelsHRM overlap.

The control unit 4 implements a writing on the road function.

There has been represented in FIG. 2B a second mode of operation of thelighting device 1 from FIGS. 1A to 1C, following on from the mode ofoperation from FIG. 2A. In this mode the vehicle equipped with thelighting device 1 enters a turn. The device 5 for detection of a turntherefore detects that the vehicle is entering a turn.

Also, the control unit 4 implements a dynamic turn lighting function by:lighting pixels of the pixelized low beam type second beam LB in thedirection of the turn, moving the oblique cut-off portion LBK_CO of thepixelized first beam HR in the direction of the turn, progressivelyextinguishing the first plurality of pixels LBK from FIG. 2A andlighting another plurality of pixels LBK of the pixelized first beam HRon the side of the turn.

In order to preserve the contrasts between the pixels of the first andsecond beams HR and LB at the level of the projection zone ZP thatenable the driver to perceive the motif, the control unit 4 then alsomoves the motif in the direction of the turn by progressivelyextinguishing the second plurality of pixels HRM from FIG. 2A andlighting another plurality of pixels HRM of the pixelized first beam HRon the side of the turn. As before, the control unit 4 reduces theluminous intensity of the pixels of the second beam LB with which thesecond plurality of pixels HRM overlap.

This therefore guarantees the preservation of the contrast by themovement of the motif at the same time as the movement of some parts ofthe pixelized low beam type beam so that the driver is not disturbed.The motif moreover remains perceptible by the driver, by remaining inposition in the projection zone from the driver's point of view.

The foregoing description explains clearly how the invention makes itpossible to achieve the objectives set for it and in particular topropose a solution enabling projection of a motif in a low beam typebeam, that motif remaining perceptible without sudden modificationduring the execution of a dynamic turn lighting function. The lightingdevice according to the invention makes it possible to preserve thecontrast characteristics enabling the motif to be perceived when thedynamic turn lighting function is used.

The invention is not limited to the embodiments specifically given inthis document by way of nonlimiting example and in particular extends toall equivalent means and any technically operative combinations of thosemeans. Accordingly the characteristics, the variants and the variousembodiments of the invention may be combined with one another in diversecombinations provided that they are not incompatible or mutuallyexclusive. There may in particular be imagined variants of the inventioncomprising only a selection of the features described provided that,according to the invention, the control unit controls at least one pixelof each of the first and second beams when the motor vehicle enters aturn so as to create a movement of said motif in the global beam.

The invention claimed is:
 1. A lighting device for a motor vehiclecomprising: a first lighting module adapted to project a pixelized firstbeam with a first resolution and a second lighting module adapted toproject a pixelized low beam type second beam with a second resolutionlower than the first resolution, the first and second lighting modulesbeing such that the first and second beams overlap vertically in part todefine a projection zone situated at the level of the overlap of thefirst and second beams and to form a global beam that includes theprojection zone, a left portion of the second beam that is notoverlapped with the first beam, and an oblique cut-off portion; and acontrol unit configured to selectively control individual pixels of thefirst and second beams so as to project a motif in the global beam,wherein the pixelized first beam includes a number of pixels greaterthan the number of pixels of the pixelized low beam type second beam,the pixelized first beam extends in the global beam above and below anupper cut-off of the pixelized low beam type second beam, with some ofthe pixels included in the pixelized first beam completely arrangedabove and adjacent to the upper cut-off of the pixelized low beam typesecond beam to form the oblique cut-off portion, and the control unit isfurther configured to selectively control the luminous intensity of thepixels of the first and second beams within the projection zone and thesome of the pixels of the first beams within the oblique cut-off portionso as to generate a contrast between the pixels of the first and secondbeams within the projection zone and the some of the pixels of the firstbeams within the oblique cut-off portion.
 2. The lighting deviceaccording to claim 1, wherein: each pixel of the pixelized first beamhas a width and/or a length strictly less than a minimum width and/or aminimum length respectively of each pixel of the pixelized low beam typesecond beam, and the pixelized first beam has a horizontal amplitudeless than the horizontal amplitude of the pixelized low beam type secondbeam.
 3. The lighting device according to claim 1, wherein the pixelizedlow beam type second beam extends horizontally and substantiallysymmetrically on respective opposite sides of a vertical axis and thefirst lighting module is such that the pixelized first beam extendshorizontally and substantially asymmetrically on respective oppositesides of that vertical axis.
 4. The lighting device according to claim1, wherein the control unit is adapted to control selectively theluminous intensity of said plurality of pixels of the first and secondbeams so that the motif is projected in the global beam by a differenceof intensity between those pixels of the first and second light beams.5. The lighting device according to claim 4, wherein the motif isdefined by a matrix of points and the control unit is adapted toselectively control the luminous intensity of the pixels of the firstand second beams within the projection zone so as to generate a contrastbetween each pair of pixels of that plurality of pixels that overlap,each contrast corresponding to a point of the matrix of points.
 6. Thelighting device according to claim 5, wherein the control unit isadapted to reduce the luminous intensity of all the pixels of thepixelized low beam type second beam at the level of said projectionzone.
 7. The lighting device according to claim 5, wherein the controlunit is adapted to control the pixels of the first beam and/or of thesecond beam when the motor vehicle enters a turn so as to modify theluminous intensity of the global beam in the direction of the turn. 8.The lighting device according to claim 7, wherein the control unit isadapted to control selectively the luminous intensity of said pluralityof pixels of the first and second beams situated in the projection zoneso as to move each contrast between a pair of pixels of those pixelsthat overlap toward another pair of pixels of those pixels that overlapin the direction of the turn.
 9. The lighting device according to claim1, wherein the first lighting module includes a matrix of monolithicelectroluminescent elements.
 10. A lighting system for a motor vehicle,the system including a lighting device according to claim 1 and a devicefor detection of a turn intended to be taken by the motor vehicle, thecontrol unit of the lighting device being adapted to receive informationfrom said turn detection device and to control the pixels of the beamsprojected by the lighting modules of the lighting device as a functionof said information.
 11. The lighting system according to claim 10,wherein the lighting system includes a device for detection of trafficconditions of the vehicle and/or for reception of information relatingto the traffic conditions of the vehicle, and in that the control unitis adapted to receive information relating to those traffic conditionsfrom said detection and/or reception device and to control selectivelysaid plurality of pixels of the first and second beams so as to projecta motif in the global beam concerning said traffic conditions.
 12. Thelighting device according to claim 6, wherein the control unit isadapted to control the pixels of the first beam and/or of the secondbeam when the motor vehicle enters a turn so as to modify the luminousintensity of the global beam in the direction of the turn.
 13. Thelighting device according to claim 1, wherein each vertical edge of eachpixel of the pixelized low beam type second beam coincides with avertical edge of a pixel of the pixeled first beam.